For silver halide color photographic materials, the system of forming a color image by using reactions between dye-forming couplers capable of respectively forming yellow, magenta, and cyan (hereinafter referred to as yellow coupler, magenta coupler, and cyan coupler, respectively) and the oxidized product of a color-developing agent is now practiced most widely.
(1) With respect to above point (a):
In recent years, for silver halide color photographic materials, studies for improving dye-forming couplers have been made vigorously with a view toward improving color reproduction and image fastness, but as yet it is difficult to say that satisfactory improvement has been made. In particular, with respect to cyan couplers, although phenol couplers or naphthol couplers are used conventionally all the time, the dyes formed from these couplers have undesirable absorption in the blue and green regions, which is a great obstacle to improvement of color reproduction. Further, since conventional cyan couplers interact with silver halide emulsions, when a photographic material containing those couplers is stored at high temperatures, the problem arises that the sensitivity lowers.
(2) With respect to above point (b):
Further, recently, cyan couplers with a new skeleton having a nitrogen-containing heterocyclic ring have been vigorously studied and various heterocyclic compounds have been suggested. For example, diphenylimidazole couplers are described in JP-A ("JP-A" means unexamined published Japanese Patent Application) No. 226653/1988 and pyrazoloazole couplers are disclosed, for example, in JP-A No. 199352/1988, 250649/1988, 250650/1988, 554/1989, 555/1989, 105250/1990, and 105251/1990. All of these couplers are asserted to be improved in color reproduction and are characterized by excellent absorption characteristics of the dyes produced therefrom.
However, the cyan dyes obtained from the above couplers have the defects that the absorption is in the short wavelength region and that the fastness to light and heat are poor, and further they have practically the serious problem that the coupling activity of the couplers themselves is low.
Incidentally, in order to improve color reproduction, use of a grain-surface-fogged emulsion of a silver halide is disclosed, for example, in JP-B ("JP-B" means examined Japanese Patent Publication) No. 35011/1984, but the emulsion is accompanied by the problems that fogging due to contact with a photosensitive emulsion takes place and that the maximum color density is lowered due to the influence of the developability of a photosensitive emulsion.
On the other hand, in the field of color photographic materials, particularly of color reversal photographic materials, in order to make up under-exposure of a color photographic material, adjustment of the sensitivity by processing, i.e., a process called "sensitizing process," is carried out. JP-B No. 38296/1989 describes that a grain-inside-fogged emulsion is contained in a color reversal photographic material for the sensitizing process. By this, however, the sensitizing processing ability can be improved, but the use conditions of the grain-inside-fogged emulsion are difficult to be optimized and, depending on the usage, the problem that the maximum color density is lowered arises.
(3) With respect to above point (c):
Further, in a silver halide color photographic material among this, an internal latent image-type emulsion whose storage stability is made high and whose sensitivity is increased has been developed. To increase further the sensitivity of the photographic material that uses this internal latent image-type emulsion, various attempts have been made. For example, U.S. Pat. Nos. 2,696,436, 3,206,313, 3,917,485, 3,979,213, and 4,623,612, and JP-B Nos. 29405/1968 and 13259/1970 describe that, by immersing a silver halide emulsion-coated sample in an AgNO.sub.3 solution or a silver halide solvent, or by carrying out chemical sensitization during the production of a silver halide emulsion and then carrying out Ostwald ripening or adding an aqueous AgNO.sub.3 solution and an aqueous soluble halide solution, a silver halide photographic material or a silver halide photographic emulsion whose internal sensitivity is high is prepared and its photographic properties are good.
Incidentally, in silver halide color, photographic materials, in recent years, new cyan couplers have been suggested for improving, for example, the color reproduction (the coupling activity and the molecular extinction coefficient of the obtained dyes) of conventional phenol- and naphthol-type cyan couplers, the fastness of the color image obtained therefrom, and the absorption characteristics of the color image obtained therefrom. For example, European Publication Patent No. 333,185 discloses 3-hydroxypyridine compounds, European Publication Patent No. 362,808 discloses 3H-2-dicyanomethylidenethiazoles, JP-A No. 32260/1989 discloses 3-dicyanomethylidene-2,3-dihydrobenzothiophene-1,1-dioxides, JP-A No. 264753/1988 and U.S. Pat. No. 4,873,183 disclose pyrazoloazoles, U.S. Pat. Nos. 4,818,672 and 4,921,783, JP-A No. 48243/1991, etc. disclose imidazoles, European Publication Patent Nos. 304,001, 329,036, and 374,781, and JP-A No. 85851/1990 disclose pyrazolopyrimidones and pyrazoloquinazolones, and European Publication Patent No. 342,637 discloses condensed ring triazoles.
However, in silver halide color photographic materials that use an internal latent image-type emulsion, the performance of these suggested new cyan couplers is not satisfactory to simultaneously satisfy, for example, the above color-forming property, color image fastness, and reproduction, and further improvement is demanded in order to put them to practical use.
That is, the dyes formed from these couplers have undesirable absorption in the blue and green regions, which is a great hindrance to improving in color reproduction. Further, since the conventional cyan couplers interact with a silver halide emulsion, there arises a problem that the sensitivity of a photographic material that uses an internal-latent-image-type emulsion containing this cyan coupler is lowered.
(4) With respect to above point (d):
In recent years, for color photographic materials, work has been done to make the color photographic material highly sensitive and to make the image quality high, in order to meet user's need. Improvement in color reproduction, as well as sharpness and graininess, is placed as a major subject in making the image quality high in color photographic materials, and research is continuing. On the other hand, improvement in development processing stability, handleability, color dye fastness, etc., of photographic materials is looked forward to, and the desire for such improvement is increasing.
With a view to improving color reproduction and image fastness, although improvement in dye-forming couplers is studied actively, it is hard to say that satisfactory improvement has been made. In particular, with respect to cyan couplers, although phenol couplers or naphthol couplers are used conventionally all the time, the dyes formed from these couplers have undesirable absorption in the blue and green regions, which is a great obstacle to improving color reproduction. Further, the fact that the molecular extinction coefficient of the cyan dye formed is small is disadvantageous to improving sharpness of images.
Further, the cyan dyes obtained from the above cyan couplers having a novel skeleton with a nitrogen-containing heterocyclic ring have the defects that the absorption lies in the range of short wavelengths and that the fastness to light and heat is poor, and practically they suffer from the serious problem that the coupling activity of the couplers themselves is small.
On the other hand, condensed ring pyrrole cyan couplers, as described in Japanese Patent Application Nos. 336807/1991 and 226325/1992, are excellent in spectral absorption properties, color image fastness, and color forming property; and it can be said that they are well expected to develop further in the future.
However, when these condensed ring pyrrole cyan couplers are used in a photographic material, they have the defect that the dissolving out of a sensitizing dye contained in the photographic material is not completed in the processing and causes color to remain in the photographic material; namely, the so-called residual color is great.
(5) With respect to above point (e):
Further, in recent years, requirements for the quality of silver halide color photographic materials are becoming more and more strict and it is required to simultaneously achieve excellent graininess, sharpness, tone reproduction, and color reproduction simultaneously.
As means of improving graininess, use is made of three silver halide emulsion layers different in sensitivity to improve graininess, which is disclosed in, for example, JP-B No. 15495/1974. However, although this method improves graininess, since the applied amount of silver halide emulsions increases to inevitably increase the thickness of the film of the emulsion layers, problems arise; that is, the development-inhibiting effect between different color-sensitive layers decreases, and the saturation of colors is degraded.
As means of enhancing the color saturation, a method is known wherein the amount of iodine in a silver halide emulsion is adjusted or a development-inhibitor-releasing compound which is the so-called DIR compound is used to inhibit the development between different color-sensitive layers.
For example, in JP-A No. 29238/1992, a method is disclosed wherein the content of iodine of the silver halide emulsion of a more sensitive layer is made smaller than the content of iodine of the silver halide emulsion of a less sensitive layer, whereby the development inhibiting between different color-sensitive layers is increased more in a highlight. However, color saturation cannot be enhanced satisfactorily by such a technique only. Further, if development inhibiting between different color-sensitive layers is made too high, though indeed the color saturation is enhanced, there is the risk that the color reproduction of subtle natural tints other than primary colors lacks fidelity, which is a problem.
(6) With respect to above point (f):
Owing to the recent technical advancement of silver halide color multilayer photographic materials, if the conditions of exposure at the time of photographing are suitable, and if, after the exposure, the conditions of processing, the conditions of printing, the conditions of screening, and the like are suitable, good color reproduction is now available. However, if these are not suitable, satisfactory color reproduction is not necessarily obtained in some cases, and all those skilled in the art are interested in that point being improved by improving color photographic materials.
The conditions of exposure at the time of photographing include, for example, excess or deficiency of the exposure amount, the exposure time, the distribution of the quantity of light of the object (the conditions of illumination), and the color temperature of the light source. Therefore, for example, for the purpose of providing a photographing photographic material that is faithful to color reproduction and whose color reproduction does not change greatly under conditions of photographing with various light sources, U.S. Pat. No. 3,672,898 discloses a method wherein the spectral sensitivity distributions of blue-, green-, and red-sensitive silver halide emulsion layers are restricted within certain ranges by combining spectral sensitizing dyes with filter dyes.
The present inventors studied various combinations of the above measures and could not find a photographic material wherein both the saturation and the fidelity of hues are satisfactory. This is because a measure is taken of making the overlap of the spectral sensitivity distributions of a red-sensitive layer and a green-sensitive layer large, and therefore mixing of colors (color contamination) due to color separation failure takes place, thereby causing the saturation to lower.
Although color separation failure can be prevented by choosing spectral sensitizing dyes wherein the ends of the spectral absorption spectrum are sharp, the sharpness is limited in actually existing spectral sensitizing dyes, and in particular it is extremely difficult to make the short wavelength ends sharp. Although, as described in U.S. Pat. No. 3,672,898, use of a filter dye can cut short wavelength ends sharply to a certain extent, it acts unfavorably at the same time because the spectral sensitivity distribution of other layers having light absorption in the part corresponding to the wavelength of that filter is affected undesirably and the sensitivity is lowered.
In color photographic materials, it is expected that various colors are reproduced to have the same brightness and colors as seen by the human eye. Colors perceived by the human vision are influenced by the spectral distribution of the absorption or emission of the object and the color temperature of the light source illuminating the object, and the difference in color temperature of a light source is perceived only as a relatively small difference by the human eye, while such a difference is detected to a greater degree than that by color photographic materials. This is because, first, the relative sensitivities of three spectrally sensitive organs of human vision change depending on the color temperature and brightness of a light source, and second the spectral sensitivity distributions of the three sensitive organs are different from the spectral sensitivity of color photographic materials. The difference between the spectral sensitivity distributions of the sensitive organs and those of color photographic materials causes such a phenomenon that, on one hand, for one color, the color reproduced by a color photographic material and the color directly observed with the naked eye are recognized as visually identical, and on the other hand, for another color, the color reproduced by a color photographic material is perceived as being completely different color by the naked eye.
To improve color reproduction, it is known to use the interlayer-inhibiting effect in the first development of a color reversal processing. For example, by giving the development-inhibiting effect from a green-sensitive layer to a red-sensitive layer, the color formation of a red-sensitive layer in white exposure can be suppressed greater than in the case of red exposure. Similarly, the development-inhibiting effect from a red-sensitive layer to a green-sensitive layer gives reproduction of green that is high in the degree of saturation.
As means of enhancing the interlayer effect, it is known to increase the iodine content of an emulsion or to use a DIR compound. However, conventionally known DIR compounds are not necessarily satisfactory in the effect for improving color reproduction and the effect for decreasing the deterioration of color reproduction is unsatisfactory when there is a great overlap of spectral sensitivity distributions.
For the purpose of providing color photographic materials wherein the change in color reproduction due to a change in the color temperature of a light source at the time of photographing is low and which have color reproduction high in saturation, JP-A No. 131937/1984 discloses a method wherein the widths of the maximum sensitivities of the spectral distributions of a blue-sensitive silver halide emulsion layer, a green-sensitive silver halide emulsion layer, and a red-sensitive silver halide emulsion layer are specified and nondiffusible DIR compounds are contained.
Although the present inventors attempted a variety of combinations of the above means, they could not obtain a photographic material that is satisfactory both in that the change in color reproduction due to a change of the color temperature of a light source at the time of photographing is small and in that even when the color temperature of a light source changes, the color reproduced is high in saturation and primary colors and neutral tints are reproduced faithfully.
(7) With respect to above point (g):
Further, when the above cyan dye-forming couplers having a novel skeleton with a nitrogen-containing heterocyclic ring are used, there is a problem with processing stability in that the photographic property is liable to variation remarkably owing to the change of the amount of sodium sulfite in a color developer, and thus it has been desired to solve this problem. In photographic processing laboratories located throughout in the world, there is a case where the state of storage of processing solutions is not good. Therefore, no problems of processing stability are recently noted as a required property for a photographic material.